JP6938926B2 - Plasma light source - Google Patents

Description

The present invention relates to a plasma light source that produces plasma light.

As one of the high-luminance light sources, a light source using plasma, a so-called plasma light source, is known. The plasma light source is attracting attention as a light source for photolithography that can obtain light such as extreme ultraviolet light. From an industrial point of view, it is desirable that the plasma light source can be miniaturized, and as candidates, a discharge generation plasma (DPP: Discharge Produced Plasma) type plasma light source and a laser generation plasma (LPP: Laser Produced Plasma) type plasma can be used. The light source is known. The light emitted from these plasma light sources (hereinafter referred to as plasma light) is pulsed light.

Control of exposure time is extremely important in photolithography. For that purpose, it is necessary not only to secure a sufficient amount (intensity) and brightness of plasma light, but also to obtain them stably. Further, since the emission time of plasma light is as short as about several μs or less, it is necessary to repeat the generation of plasma (that is, the emission of plasma light) at high speed.

A plasma light source related to the above is disclosed in Patent Document 1. The plasma light source in the same document is a plasma light source that employs a plasma focus method, which is a type of DPP method, and is a pair of coaxial electrodes that are arranged opposite to each other with respect to a plane of symmetry and generate and confine plasma that emits extreme ultraviolet light. And a voltage application device that applies a discharge voltage to each coaxial electrode. Each coaxial electrode has a rod-shaped center electrode and a plurality of external electrodes arranged at regular intervals from the center electrode and in the circumferential direction of the center electrode.

In the plasma light source of Patent Document 1, a pulsed voltage is further applied in a state where a high voltage is applied between the center electrode and the external electrode, or laser ablation is performed at any part of the coaxial electrode. Induces an initial discharge between both electrodes. The initial discharge is formed in an annular shape centered on the center electrode, and moves toward the tip of the center electrode by electromagnetic force while promoting the generation and growth of plasma. Further, the plasma of each coaxial electrode receives electrical energy and fuses, is confined, and converges between the coaxial electrodes, resulting in high temperature and high density. As a result, light including extreme ultraviolet light is emitted.

Japanese Unexamined Patent Publication No. 2013-089634

In the plasma light source of Patent Document 1, the initial discharge generated at each coaxial electrode moves while growing into an annular plasma, and then fuses with each other between the coaxial electrodes to become high temperature and high density. The electric energy supplied to the plasma is generated by a voltage application device, and its value is the product of the voltage applied between the center electrode and each external electrode and the current flowing between the center electrode and each external electrode. Is proportional to.

On the other hand, while the plasma is heated by the electric energy, the tip of the center electrode is also heated by the current of the electric energy. The value of the current flowing through the center electrode is the value obtained by multiplying the value of the current flowing through each external electrode by the number of external electrodes. Therefore, the center electrode is more easily heated than the external electrode, and the temperature rises remarkably. Moreover, the current flowing through (or from) the plasma is concentrated at the tip of the center electrode. Therefore, it can be said that the tip portion is more susceptible to heat damage than its surroundings. The damage referred to here includes not only structural changes but also physical changes (for example, phase transition).

For example, when the shape of the tip of the center electrode changes due to melting, chipping, cracking, etc., the electric field distribution around it changes and the symmetry is broken. The symmetry breaking of the electric field distribution affects the contraction of the plasma, making it difficult to heat or maintain the desired temperature. That is, there is a concern that the intensity of plasma light per light emission is insufficient. In addition, if the physical properties of the tip of the center electrode change, there is a concern that the life (operating time) of the plasma light source will be shortened due to its vulnerability.

Therefore, the present invention prevents thermal damage to the center electrode of each coaxial electrode in a plasma light source provided with a pair of coaxial electrodes that are arranged opposite to each other with respect to the plane of symmetry and that generate and confine plasma that radiates plasma light. The purpose is.

One aspect of the present invention is a plasma light source, which has a center electrode extending on a single axis and an external electrode provided so as to surround the outer periphery of the center electrode, and is arranged to face each other with a plane of symmetry in between. For each of the coaxial electrodes, a pair of coaxial electrodes that generate and confine the plasma that emits light, a medium holding portion that holds the medium of the plasma supplied between the center electrode and the external electrode, and each of the coaxial electrodes. A voltage applying device for applying a discharge voltage, a nozzle provided in a hole extending from the base end to the tip of the center electrode at a distance from the inner wall of the hole, and a refrigerant for supplying a refrigerant to the supply path. A feeder is provided, the nozzle has a refrigerant supply path that opens toward the tip of the center electrode, and the outer peripheral surface of the nozzle and the inner wall of the hole are of the refrigerant communicating with the supply path. the discharge passage is formed, the supply amount of the refrigerant by the refrigerant dispenser, gist that you have been set to a value to maintain nucleate boiling region from nucleate boiling point of the refrigerant in the center electrode within up to maximum heat flux point And.

The outer peripheral surface of the nozzle may have an uneven portion.

According to the present invention, in a plasma light source provided with a pair of coaxial electrodes that are arranged opposite to each other with respect to a plane of symmetry and that generate and confine plasma that radiates plasma light, thermal damage to the center electrode of each coaxial electrode is prevented. can do.

It is a schematic block diagram (cross-sectional view) of the plasma light source which concerns on embodiment of this invention. It is a figure which shows the electric system of the plasma light source which concerns on embodiment of this invention. It is a figure which shows the III-III cross section of FIG. It is a figure for demonstrating the cooling operation by the center electrode, the nozzle and the refrigerant which concerns on embodiment of this invention, (a) is the sectional view of the center electrode and nozzle including a central axis, (b) is IVB of (a). It is a figure which shows the −IVB cross section. It is a figure which shows the modification of the nozzle which concerns on embodiment of this invention, (a) is the figure which shows the 1st modification of a nozzle, (b) is the figure which shows the 2nd modification of a nozzle.

Hereinafter, the plasma light source according to the embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the same reference numerals are given to common parts in each figure, and duplicate description is omitted.

FIG. 1 is a schematic configuration diagram (cross-sectional view) showing a plasma light source according to the present embodiment. FIG. 2 is a diagram showing an electrical system of the plasma light source. FIG. 3 is a diagram showing a cross section III-III of FIG. As shown in FIG. 1, the plasma light source of the present embodiment includes a pair of coaxial electrodes 10 and 10, a medium holding portion 17, a voltage applying device 20, a laser device 30, and a refrigerant supply device 40.

The pair of coaxial electrodes 10 and 10 are installed in the vacuum chamber 5 and are installed at positions symmetrical with respect to the plane of symmetry 1. That is, this plasma light source is a light source that employs a facing plasma focus method. The pair of coaxial electrodes 10 and 10 are installed at regular intervals with the plane of symmetry 1 interposed therebetween, and the tip side (the side on which the planar discharge 2b described later is discharged) faces each other.

A high voltage required for discharging is applied to the coaxial electrodes 10 and 10 by the voltage applying device 20. With the voltage applied to the coaxial electrodes 10 and 10, the medium holding portion 17 is irradiated with the laser light 32 from the laser device 30. The laser light 32 evaporates the plasma medium 6 in the medium holding portion 17. The evaporated plasma medium (that is, medium gas) 6 is supplied between the center electrode 11 and the external electrode 12 of each coaxial electrode 10. That is, the plasma medium 6 is diffused between the center electrode 11 and the external electrode 12 of each coaxial electrode 10 by the ablation of the laser beam 32.

When the plasma medium 6 diffuses between the center electrode 11 and the external electrode 12, an initial discharge (initial plasma) 2a is induced between the center electrode 11 and the external electrode 12, and the plasma medium 6 is ionized. Further, the coaxial electrodes 10 and 10 grow the initial discharge 2a into a planar discharge 2b to generate a plasma 3 between them and confine it. The plasma 3 confined between the coaxial electrodes 10 and 10 is heated by receiving electrical energy from the coaxial electrodes 10 and 10 and emits plasma light 8. The planar discharge is a planar discharge current that spreads two-dimensionally, and is also called a current sheet or a plasma sheet.

Each coaxial electrode 10 includes a center electrode 11 and a plurality of external electrodes 12 provided so as to surround the outer periphery of the center electrode 11. The center electrode 11 and the external electrode 12 are supported by an insulator (not shown) such as ceramic.

The center electrode 11 is a rod-shaped conductor extending on the central axis Z with a single axis ZZ common to each coaxial electrode 10 as a central axis (hereinafter, this axis is referred to as a central axis Z). .. The diameter of the center electrode 11 decreases toward the plane of symmetry 1. For example, the center electrode 11 is formed in a substantially conical shape with the tip end portion 11a at the apex angle. The maximum diameter of the center electrode 11 is, for example, 5 mm. The center electrode 11 is formed by using a material having resistance to high temperature, for example, a refractory metal such as W (tungsten) or Mo (molybdenum). The center electrode 11 may be a rod-shaped electrode having a constant diameter.

The center electrode 11 has a tip portion (tip) 11a facing the plane of symmetry 1, a side surface 11b formed around the central axis Z, and a base end portion (base) located opposite to the tip portion 11a with the side surface 11b interposed therebetween. It has an end) 11c. The tip portion 11a has a hemispherical curved surface facing the plane of symmetry 1. However, the shape of the surface facing the plane of symmetry 1 is not limited to a curved surface, and may be a simple plane. Further, a recess (not shown) recessed along the central axis Z may be provided.

As shown in FIG. 1, the external electrode 12 is a rod-shaped conductor extending along the center electrode 11 to the plane of symmetry 1. The diameter of the external electrode 12 is, for example, 3 mm. The external electrode 12 is inclined with respect to the central axis Z so as to approach the central axis Z as it approaches the plane of symmetry 1. The distance between the center electrode 11 and the external electrode 12 may be constant, and may be smaller as the distance approaches the plane of symmetry 1.

As shown in FIG. 3, the external electrodes 12 are arranged at each angle θ along the circumferential direction of the center electrode 11. In other words, each external electrode 12 is arranged parallel to the center electrode 11 and surrounds the center electrode 11. In the example shown in FIG. 3, six external electrodes 12 are arranged around the center electrode 11 at intervals of 60 °. The material of the external electrode 12 is a conductive substance having resistance to high temperatures, like the center electrode 11. The end face of the external electrode 12 facing the plane of symmetry 1 may be either a curved surface or a flat surface.

It is desirable that the external electrodes 12 are installed at equal intervals around the center electrode 11. For example, from the viewpoint of processing and assembly, or from the viewpoint of ease of forming the planar discharge 2b, it is desirable that each external electrode 12 is installed at a position rotationally symmetric with respect to the center electrode 11. However, the present invention is not limited to such sequences. Further, the number of the external electrodes 12 is not limited to the six shown in FIG. 3, and is appropriately set according to the size and shape of the center electrode 11 and the external electrode 12, the distance between the two, and the like.

The medium holding unit 17 holds the plasma medium 6 supplied between the center electrode 11 and the external electrode 12. The medium holding portion 17 is formed as a container for holding the plasma medium 6 or the plasma medium 6 itself, and is located between two adjacent external electrodes 12 when viewed from the center electrode 11. Further, the medium holding portion 17 is installed outside the coaxial electrode 10. The “outside” in this case means, for example, a space outside the region surrounded by the center of each external electrode 12.

As shown in FIG. 3, it is desirable that a plurality of medium holding portions 17 are provided around the coaxial electrode 10 and are located at point-symmetrical or rotationally symmetric positions around the center electrode 11. That is, it is desirable that the supply points of the plasma medium 6 to the coaxial electrode 10 are distributed symmetrically with respect to the center electrode 11. However, the installation location of the medium holding portion 17 is not limited to these. Further, in each case, in consideration of the emission angle characteristics of the plasma medium 6, the surface of the plasma medium 6 including the irradiation point of the laser beam 32 is the space between the external electrode 12 and the center electrode 11 or the center electrode 11. It is suitable.

The composition of the plasma medium 6 is selected according to the required wavelength of light. The plasma medium 6 contains, for example, Li (lithium) and Sn (tin) when 13.5 nm ultraviolet light is required, and gadolinium (Gd) and terbium (Tb) when 6.7 nm ultraviolet light is required. Including Bi (bismuth) when ultraviolet light of 3 to 4 nm is required.

4A and 4B are views for explaining a cooling operation by a center electrode, a nozzle, and a refrigerant according to the present embodiment. FIG. 4A is a cross-sectional view of a center electrode 11 including a central axis Z and a nozzle 14, and FIG. 4B is a cross-sectional view. It is a figure which shows the IVB-IVB cross section of (a). As shown in FIG. 4A, a hole 13 is formed in the center electrode 11. The hole 13 extends from the base end portion 11c of the center electrode 11 toward the tip end portion 11a, and has a bottom surface 13b in the vicinity of the tip end portion 11a of the center electrode 11. A nozzle 14 is provided in the hole 13.

The hole 13 has a shape that allows a desired cooling capacity to be obtained while considering the outer shape and dimensions of the nozzle 14. For example, as shown in FIG. 4A, when the nozzle 14 is formed in a substantially conical shape having an opening 14a at an apex angle, the hole 13 also has a corresponding similar shape. As shown by the white arrows in FIG. 4A, the refrigerant is discharged from the opening 14a of the nozzle 14 toward the bottom surface 13b via the supply path 15, and then reverses and flows through the discharge path 16. do. In order to facilitate this flow, it is desirable that the bottom surface 13b is a concave surface recessed toward the tip end portion 11a of the center electrode 11.

The nozzle 14 is a pipe extending along the central axis Z, and has a refrigerant supply path 15 that opens toward the tip end portion 11a of the central electrode 11 inside the nozzle 14. Further, the nozzle 14 is provided at a distance from the inner wall 13a of the hole 13. In other words, the nozzle 14 has dimensions and a structure in which a space is formed between the nozzle 14 and the inner wall 13a of the hole 13. As a result, the outer peripheral surface 14b of the nozzle 14 forms the refrigerant discharge path 16 communicating with the supply path 15 together with the inner wall 13a of the hole 13.

The holes 13 and nozzles 14 of the present embodiment have a shape symmetrical with respect to the central axis Z and are installed concentrically. Therefore, the supply path 15 and the discharge path 16 also have a shape (space) that is axisymmetric with respect to the central axis Z.

As described above, the plasma light source of the present embodiment includes the refrigerant supply device 40. The refrigerant supply device 40 is composed of a pump (not shown) and a cooler (not shown), and is connected to the supply path 15 and the discharge path 16 via a pipe 42. The refrigerant supply device 40 cools the refrigerant discharged from the discharge path 16 and supplies it to the supply path 15. The refrigerant supply device 40 sets the supply amount of the refrigerant to a value that maintains the nucleate boiling region from the nucleate boiling limit point of the refrigerant to the maximum heat flux point in the center electrode 11. With this setting, heat transfer to the refrigerant is most efficiently achieved.

The refrigerant of this embodiment is water. When the center electrode 11 is not grounded, a material having an insulating property such as fluororesin is used for the pipe 42 in the vacuum tank 5 in order to prevent a short circuit between the center electrode 11 and the vacuum tank 5 via water. Things are used. Further, the pipe 42 in the vacuum chamber 5 has a length such that the electric resistance of the water flowing through the pipe 42 can maintain the electrical insulation between the center electrode 11 and the vacuum chamber 5. In addition, in order to increase the electrical resistance of water, a deionization treatment device (not shown) may be installed in the middle of the pipe 42. Further, as the refrigerant, alcohol-mixed water or a fluorine-based inert liquid may be used.

Next, the electric system in the plasma light source of the present embodiment will be described. As shown in FIG. 2, the plasma light source includes a voltage applying device 20 connected to each coaxial electrode 10. The voltage application device 20 applies a discharge voltage having the same polarity or the opposite polarity to each coaxial electrode 10.

The voltage application device 20 includes a high voltage power supply 22. The positive electrode side of the high voltage power supply 22 is connected to the center electrode 11 of the coaxial electrode 10, and the negative electrode side of the high voltage power supply 22 is connected to the external electrode 12. The high-voltage power supply 22 applies a discharge voltage (for example, 5 kV) between the center electrode 11 and the external electrode 12. The polarity of the discharge voltage may be positive or negative with respect to the center electrode 11.

As described above, a plurality of external electrodes 12 are provided around each center electrode 11. In order to obtain an ideal discharge, it is necessary for a discharge to occur between all the external electrodes 12 and the center electrode 11. Moreover, it is desirable that these discharges are spatially evenly distributed around the center electrode 11. However, the discharge energy supplied from the high-voltage power supply 22 tends to be preferentially consumed over the first generated discharge, and in this case, it becomes difficult to generate a plurality of discharges at different locations substantially simultaneously.

Therefore, the voltage application device 20 of the present embodiment includes an energy storage circuit 24 that stores the discharge energy of the discharge voltage for each external electrode 12. The energy storage circuit 24 is composed of a plurality of capacitors C that individually connect the center electrode 11 and each external electrode 12 as shown in FIG. 2, for example. Each capacitor C has a capacitance capable of passing a discharge current of about 2 kA at the peak of discharge, and is connected between the outputs of the high-voltage power supply 22.

By providing the capacitor C for storing the discharge energy for each external electrode 12 in this way, it is possible to generate a discharge in all the external electrodes 12. That is, it is possible to prevent the discharge energy from being excessively consumed by the first generated discharge, and it is possible to generate a planar discharge 2b over the entire circumference of the center electrode 11.

Further, the voltage application device 20 may include a discharge current blocking circuit 26 that prevents the discharge current from returning. The discharge current blocking circuit 26 is composed of an inductor L that connects each external electrode 12 and the voltage applying device 20 as shown in FIG. 2, for example. Since the inductor L has a sufficiently high impedance with respect to the discharge current, the discharge current via the center electrode 11 and the external electrode 12 can be returned to the energy storage circuit 24 which is the source of the discharge current. That is, in order to prevent the discharge energy stored in each capacitor C from being supplied to the external electrodes 12 other than the external electrode 12 directly connected to the capacitor C, the discharge generation distribution in the circumferential direction of the center electrode 11 is biased. Can be prevented from occurring.

As described above, the plasma light source of the present embodiment includes the laser device 30. The laser device 30 emits the medium of the plasma 3 by irradiating the center electrode 11 of each coaxial electrode 10 with the laser light 32, and cooperates with the voltage application device 20 to discharge the initial discharge of the plasma 3 (initial plasma). ) Generate 2a. The laser device 30 is, for example, a YAG laser, and outputs a fundamental wave or a double wave thereof as a short pulse laser beam 32 for ablation. The laser beam 32 is branched by an optical element such as a half mirror, and is irradiated to the medium holding portion 17. In the medium holding portion 17 irradiated with the laser light 32, the plasma medium 6 is emitted as neutral particles or ions by the ablation of the laser light 32. The laser light 32 is repeatedly irradiated to the plasma medium 6 at a frequency of about several kHz, and ablation of the plasma medium 6 is generated each time the laser light 32 is irradiated.

The operation of the plasma light source of the present embodiment up to the emission of plasma light will be described.
First, with the pair of coaxial electrodes 10 installed in the vacuum chamber 5, the inside of the vacuum chamber 5 is maintained at a temperature and pressure suitable for generating plasma 3. Next, a discharge voltage having the same polarity or the opposite polarity is applied to each coaxial electrode 10 by the voltage applying device 20.

A laser beam 32 is applied to each medium holding portion 17 in a state where a discharge voltage is applied to each coaxial electrode 10. In each coaxial electrode 10, the plasma medium 6 becomes a neutral gas or an ion and is emitted in a large amount by this irradiation.

On the other hand, when the laser beam 32 is irradiated, the discharge voltage from the voltage applying device 20 has already been applied between the center electrode 11 and the external electrode 12 of each coaxial electrode 10. Therefore, the occurrence of ablation induces an initial discharge 2a between the center electrode 11 and each external electrode 12.

The initial discharge 2a proceeds toward the plane of symmetry 1. Further, the initial discharge 2a grows into a planar discharge 2b distributed over the entire circumference of the center electrode 11 while taking in the plasma medium 6 emitted by the ablation. The planar discharge 2b moves in the direction of being discharged from the coaxial electrode 10 (that is, the direction toward the plane of symmetry 1) by the self-magnetic field. The planar discharge 2b at this time is distributed in a substantially annular shape when viewed from the central axis Z.

When the planar discharge 2b reaches the tip of the coaxial electrode 10, the starting point of the discharge current of the planar discharge 2b shifts from the circumferential side surface of the center electrode 11 to the tip portion 11a. In other words, the discharge current flows out intensively from the tip portion 11a. Due to this current concentration, the current density around the tip 11a rises sharply, and the plasma medium 6 around the tip 11a sandwiched between the pair of planar discharges 2b becomes high density and high temperature.

Further, since this phenomenon proceeds at each coaxial electrode 10 sandwiching the plane of symmetry 1, the plasma medium 6 is pushed out from one coaxial electrode 10 toward the other coaxial electrode 10. As a result, the plasma medium 6 receives electromagnetic pressure from both directions along the central axis Z and moves to an intermediate position where the coaxial electrodes 10 face each other (that is, the plane of symmetry 1 of the central electrode 11), and the plasma medium 6 moves. A single plasma 3 containing the above is formed.

While the planar discharge 2b is generated, the current of each planar discharge 2b is concentrated on the tip portion 11a of each center electrode 11. Therefore, an electromagnetic pressure is applied to the plasma 3 around the tip portion 11a, and the density and temperature of the plasma 3 are increased. That is, the ionization of the plasma medium 6 proceeds. As a result, the plasma light 8 is emitted from the plasma 3. In this state, the voltage applying device 20 continues to supply electrical energy to the plasma 3. With this energy supply, the plasma light 8 can be generated for a long time.

Since the above series of processes are repeated at a frequency of several kHz, the tip portion 11a of the center electrode 11 is heated by the current 4 (see FIG. 4A) supplied to the plasma 3. That is, the heat 7 (see FIG. 4A) at that time is intensively generated at the tip end portion 11a and propagates while diffusing toward the base end portion 11c of the center electrode 11.

On the other hand, while the plasma light source is in operation, the refrigerant flows through the center electrode 11. Therefore, the low-temperature refrigerant is discharged from the opening 14a of the nozzle 14 via the supply path 15 and is supplied to the vicinity of the bottom surface 13b of the hole 13. The heat 7 from the tip portion 11a is absorbed by the refrigerant via the bottom surface 13b. That is, the refrigerant cools the tip portion 11a. The refrigerant that has absorbed heat is discharged to the outside of the center electrode 11 via the discharge path 16 and returns to the refrigerant supply device 40. After that, the refrigerant is cooled again and supplied to the supply path 15. As a result, the center electrode 11 can be prevented from being damaged by heat without being excessively heated.

Further, the supply path 15 and the discharge path 16 have a shape (space) that is axisymmetric with respect to the central axis Z, and these are located concentrically. That is, the supply path 15 and the discharge path 16 form a coaxial double circular tube that functions as a cooling flow path. In particular, the width of the discharge path 16 in the radial direction of the center electrode 11 is constant in the circumferential direction of the center electrode 11. Therefore, the flow rate of the heat medium flowing through the discharge path 16 does not depend on the circumferential direction of the center electrode 11, and a uniform endothermic performance of the heat medium can be obtained around the central axis Z. That is, it is possible to prevent the excessively heated portion of the center electrode 11 from being unevenly distributed and increasing.

5A and 5B are views showing a modified example of the nozzle 14 according to the present embodiment, FIG. 5A is a diagram showing a first modified example of the nozzle 14, and FIG. 5B is a diagram showing a second modified example of the nozzle 14. be. As shown in these modifications, the outer peripheral surface 14b of 14 may have an uneven portion 14c. The uneven portion 14c has, for example, fins protruding outward in the radial direction of the nozzle 14 from the outer peripheral surface 14b. The fin may be composed of a plurality of protrusions as shown in FIG. 5A, or may be spirally extended on the outer peripheral surface 14b as shown in FIG. 5B. Alternatively, the uneven portion 14c may have a groove or a recess (not shown) recessed inward in the radial direction of the nozzle 14 from the outer peripheral surface 14b. Grooves or recesses (not shown) are formed, for example, in place of the protrusions of FIG. 5 (a) and the fins of FIG. 5 (b). The uneven portion 14c expands the contact area of the nozzle 14 with the heat medium flowing through the discharge path 16. That is, the uneven portion 14c promotes heat exchange between the heat medium flowing through the supply path 15 and the heat medium flowing through the discharge path 16 via the nozzle 14. This promotes cooling of the center electrode 11.

The present invention is not limited to the above-described embodiment, but is shown by the description of the scope of claims, and further includes all modifications within the meaning and scope equivalent to the description of the scope of claims.

1 ... Symmetrical plane, 2a ... Initial discharge, 2b ... Planar discharge, 3 ... Plasma, 4 ... Current, 5 ... Vacuum chamber, 6 ... Plasma medium, 7 ... Heat, 8 ... Plasma light, 10 ... Coaxial electrode, 11 ... Center electrode, 12 ... External electrode, 13 ... Hole, 14 ... Nozzle, 15 ... Supply path, 16 ... Discharge path, 17 ... Medium holder, 20 ... Voltage application device, 22 ... High-voltage power supply, 24 ... Energy storage circuit, 26 ... Discharge current blocking circuit, 30 ... Laser device, 32 ... Laser light, 40 ... Refrigerator supply, 42 ... Piping, Z ... Central axis (axis)

Claims (2)

A pair of coaxial cables having a center electrode extending on a single axis and an external electrode provided so as to surround the outer periphery of the center electrode, arranged opposite to each other with a plane of symmetry in between, and generating and confining plasma that radiates plasma light. Shaped electrode and
A medium holding portion that holds the medium of the plasma supplied between the center electrode and the external electrode, and
A voltage application device that applies a discharge voltage to each of the coaxial electrodes,
A nozzle provided in the hole extending from the base end to the tip end of the center electrode at a distance from the inner wall of the hole .
A refrigerant supply device for supplying a refrigerant to the supply path and a refrigerant supply device are provided.
The nozzle has a refrigerant supply path that opens toward the tip of the center electrode.
The outer peripheral surface of the nozzle and the inner wall of the hole form a refrigerant discharge path communicating with the supply path .
The amount of refrigerant supplied by the refrigerant feeder is set to a value that maintains the nucleate boiling region from the nucleate boiling limit point of the refrigerant to the maximum heat flux point in the center electrode . The plasma light source according to claim 1, wherein the outer peripheral surface of the nozzle has an uneven portion.

Images